Conventional multi-stage depressed collectors (MSDCs) used with electron tubes of high power amplifiers such as a traveling wave tube (TWT), klystron, extended interaction klystron (EIK), inductive output tube (IOT), and a coupled cavity traveling wave tube (CCTWT) use a fixed depression ratio, such as thirty three percent and sixty six percent (33/66). This ratio(s) is chosen to work at the maximum power of the device, usually saturation. If the depression voltage is too close to the cathode voltage, electrons will be returned to the body, causing thermal overload and/or spurious signals. FIG. 1 shows schematically a conventional high power amplifier 100 having a cathode 102, an anode 104, and a multi-stage depressed collector consisting of two collector stage electrodes, 106a and 106b. During normal operation at maximum power (saturation), the voltage of first collector stage electrode 106a is kept at about 66% of the cathode potential, while second (106b) collector stage electrode is kept at about 33% of the cathode potential. These percentages are provided by fixed power sources 108 and 110, and this is implemented irrespective of the power level of operation.